Classic case of slowdown due to global rounding mode is
int=float;
the rules say you chop, and on the 80×87 this forces rounding mode to change twice, which costs a few
dozen cycles; see http://stereopsis.com/FPU.html.
There is a special optimization https://docs.microsoft.com/en-us/cpp/build/reference/qifist-suppress-ftol?view=vs-2017 to avoid this double change and allow rounding.
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This reply was modified 5 years, 9 months ago by
gideony2.